(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

One of those annoying questions that should be simple, but that I've forgotten how to do:

Two lines are given by the equationsr1=a+lpandr2=b+mq. Find the condition for the lines to cross, and find there position of intersection.

2. Relevant equations

3. The attempt at a solution

I've done the first bit: (a-b).(p*q)=0 where * means the cross product. But I can't find a way of doing the second bit (find the point of intersection), I'd know how to do it if the actual vectors were given, but how do you write in in a nice vector form?

Thanks

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# Vectors/ lines

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